Alcohol is a depressant, so it has to effect your thinking, and as a result, your game.
One of my favourite times to play, is late on a Friday night, when people have been out drinking, and come home, and play poker. It's helpful in tournaments, but cash games are the best for this.
Being drunk, is not conducive to lengthy tournament play, but cash games are very conducive to short term play, and that's were they head.